Ortho-(2,6-dichlorophenyl)aminophenylacetic acid and its pharmaceutically acceptable salts are known beta-blocking compounds, useful in the treatment of inflammation. Sodium ortho(2,6-dichlorophenyl)aminophenylacetate, also commonly known as diclofenac sodium, has been shown, for example, in pharmacological studies to possess potent anti-inflammatory and analgesic properties. See, for example, Riess et al., Scand. J. Rheumatol. Suppl., Vol. 22, pp. 17-29 (1978). The use of diclofenac sodium in the form of an aqueous solution in the treatment of ocular inflammation has also been shown. See, for example, M. Agata et al., Nihon Ganka Gakkai [Acta Soc. Ophthalmol. Japan], Vol. 87, pp. 19-28 (1983), and M. Agata et al., Nihon Ganka Gakkai [Acta Soc. Ophthalmol. Japan], Vol. 88, No. 6, pp. 61-66 (1984).
Aqueous solutions of pharmaceutically acceptable salts of ortho-(2,6-dichlorophenyl)aminophenylacetic acid are useful in the treatment or control of ocular inflammation in mammals, including man, by topical application of an effective amount thereof to the eye, and are particularly advantageous in the control of post-operative inflammation, inter alia, of the type associated with cataract removal, intra-ocular lens replacement or laser tubeculoplasty; for the control of inflammation associated with bacterial conjunctivitis; for the symptomatic relief of vernal conjunctivitis; and for the prevention of miosis in patients undergoing surgery for cataract removal.
Unfortunately, aqueous solutions of ortho-(2,6-dichlorophenyl)aminoacetic acid and salts thereof can slowly decompose into byproducts. Thus, diclofenac sodium aqueous solutions can slowly degrade, for example, upon storage into the corresponding 1-(2,6-dichlorophenyl)-2-indolinone and the like, depending upon the solution temperature and hydrogen ion concentration. See, for example, Larsen et al., Arch. Pharm. Chemi, Sci. Ed., Vol. 8, pp. 100-108 (1980).
In U.S. Pat. No. 4,230,724, ethylenediamine tetraacetic acid is mentioned as a stabilizing chelating agent for 2-(2-fluoro-4-biphenylyl) propionic acid, i.e. florbiprofen, ophthalmic compositions. Also in U.S. Pat. No. 4,474,811, the disodium salt of ethylenediamine tetraacetic acid is recited as a preservative in ophthalmic solutions containing mixtures of 2-(2-fluoro-4-biphenylyl) propionic acid and a cyclodextrin. However, Example 1 of this latter patent illustrates no differences in stability of the compound solutions with and without the disodium salt of ethylenediamine tetraacetic acid in one month storage tests, U.S. Pat. No. 4,474,811 at column 8, lines 32-39.
It is an object of the present invention to provide stable aqueous solutions of pharmaceutically acceptable salts of ortho-(2,6-dichlorophenyl)aminophenylacetic acid containing an effective stabilizing amount of a pharmaceutically acceptable salt of ethylenediamine tetraacetic acid.
It is a further object of the present invention to provide a method of treating or controlling ocular inflammation in a mammal by topical administration of such stabilized aqueous solutions of a pharmaceutically acceptable salt of ortho-(2,6-dichlorophenyl)aminophenylacetic acid.
These and other objects of the present invention will become apparent from the following disclosures.